The present invention deals with the formation of xcex3-butyrolactone and substituted xcex3-butyrolactones of the general formula 
where R1 and R2 may be hydrogen, alkyl, cycloalkyl and aryl and may further contain functionalities such as ether and ester groups.
The invention is characterised by contacting an olefin of the general formula R1CHCH2, a carboxylic acid of the general formula R2CH2COOH and oxygen in the vapour phase with a catalyst. The reaction which runs according to the following equation 
is carried out at a temperature of between 120xc2x0 C. and 320xc2x0 C. With oxygen as the electron acceptor (stoichiometric oxidant) water is formed as a by-product. The process may be carried out in continuous mode with the feed gas consisting of olefin, carboxylic acid, oxygen and optionally a diluent or it may be carried out in a recycling mode, where the catalyst acts as oxygen carrier.
The process may be carried out in a fixed-bed reactor, a fluid-bed reactor, a Riser reactor and other reactors, which may prove practical.
The catalyst is characterised by containing manganese and basic metal oxides (alkali, alkaline earth, rare earth and other basic oxides). The catalyst may be prepared by impregnation on a suitable support material and by precipitation of manganese salts together with other components.
The following example serves to demonstrate the concept and scope of the reaction.
A mixture of 1-octene and acetic acid was evaporated in a stream of nitrogen through a fixed bed of catalyst placed in a glass reactor mounted in a tubular oven. Experiments were carried out at 250-350xc2x0 C. and normal pressure. The catalyst was an alumina supported, alkali promoted manganese catalyst. The effluent gas was passed through a condenser and the condensate was collected and analysed. The catalytic formation of n-hexyl xcex3-butyrolactone (R1=C6H13, R2=H) according to the equation 
was demonstrated by: (a) continuous formation of product (detected by GC/GC-MS) within a limited period of time; (b) ceasing product formation after this period and (c) renewed product formation after regeneration of the catalyst with air at 300-350xc2x0 C.